An off-road vehicle may be defined as a road vehicle having some off-road capability, such as the provision of all wheel drive. Off road vehicles are often required to travel through water to reach their intended destination. Travel through deep water (typically over about 0.3 m in depth) is known as “wading”. Known off-road vehicles are designed to wade, and comprise suitably sealed closures to avoid ingress of water into the passenger compartment. The engine air intake is positioned at an elevated position (normally directly in front of and below the windscreen) to prevent water being ingested into the engine, and this intake will often dictate the maximum level of water relative to the body that the vehicle can wade through without risking water ingestion and engine damage.
Prior art methods of determining if the water level is safe to wade through include referring to depth gauges, e.g. permanent graduated poles situated within the water in the case of fords and measurement of the depth by the driver using a partially submerged stick or pole.
The former method requires such a pole to be present, and the latter method involves the driver exiting the vehicle. The latter method in particular will often not reveal the deepest point unless the driver wades in, which is undesirable and dangerous.
Both methods only reveal the absolute depth of the water (from the ground to the water surface). This is often not sufficient to make an accurate assessment of the vehicle's capability to pass. The knowledge that the driver requires is, instead, what the water level is relative to a point on the vehicle body (e.g. the air intake). The distance between the bottom of the vehicle tyres and the air intake is variable (due to suspension travel, tyre pressure variations etc) and as such with known methods the driver must take account of a potential margin of error in making his decision. This is undesirable as the driver may decide not to proceed through water which the vehicle is capable of wading through. Known methods are practicable only in daylight.
An aim of the present invention is to at least mitigate the above mentioned problems.